public void EDR_QuantiliesShouldBeBasedOnWeights()
{
var reservoir = new DefaultForwardDecayingReservoir(
Constants.ReservoirSampling.DefaultSampleSize,
Constants.ReservoirSampling.DefaultExponentialDecayFactor,
_clock,
_scheduler);
for (var i = 0; i < 40; i++)
{
reservoir.Update(177);
}
_clock.Advance(TimeUnit.Seconds, 120);
for (var i = 0; i < 10; i++)
{
reservoir.Update(9999);
}
reservoir.GetSnapshot().Size.Should().Be(50);
// the first added 40 items (177) have weights 1
// the next added 10 items (9999) have weights ~6
// so, it's 40 vs 60 distribution, not 40 vs 10
reservoir.GetSnapshot().Median.Should().Be(9999);
reservoir.GetSnapshot().Percentile75.Should().Be(9999);
}
public void EDR_SpotLift()
{
var reservoir = new DefaultForwardDecayingReservoir(
Constants.ReservoirSampling.DefaultSampleSize,
Constants.ReservoirSampling.DefaultExponentialDecayFactor,
_clock,
_scheduler);
var valuesRatePerMinute = 10;
var valuesIntervalMillis = (int)(TimeUnit.Minutes.ToMilliseconds(1) / valuesRatePerMinute);
// mode 1: steady regime for 120 minutes
for (var i = 0; i < 120 * valuesRatePerMinute; i++)
{
reservoir.Update(177);
_clock.Advance(TimeUnit.Milliseconds, valuesIntervalMillis);
}
// switching to mode 2: 10 minutes more with the same rate, but larger value
for (var i = 0; i < 10 * valuesRatePerMinute; i++)
{
reservoir.Update(9999);
_clock.Advance(TimeUnit.Milliseconds, valuesIntervalMillis);
}
// expect that quantiles should be more about mode 2 after 10 minutes
reservoir.GetSnapshot().Median.Should().Be(9999);
}
public void EDR_NonzeroMinimumSampleWeightEvictsSamplesDuringRescale()
{
var reservoir = new DefaultForwardDecayingReservoir(
10,
AppMetricsReservoirSamplingConstants.DefaultExponentialDecayFactor,
0.1,
_clock,
new TestReservoirRescaleScheduler(_clock, TimeSpan.FromSeconds(200)));
// First set of values will have the weight equal to 1
for (var i = 0; i < 5; i++)
{
reservoir.Update(100);
}
_clock.Advance(TimeUnit.Seconds, 120);
// The second set of values will have weights equal to about 6
for (var i = 0; i < 5; i++)
{
reservoir.Update(1000);
}
reservoir.GetSnapshot().Size.Should().Be(10);
// Trigger rescale
_clock.Advance(TimeUnit.Seconds, 120);
// New weights for the two value sets will be about 0.03 and 0.16 respectively,
// so a minimum weight of 0.1 should have eliminated the first set.
reservoir.GetSnapshot().Size.Should().Be(5);
reservoir.GetSnapshot().Values.Should().OnlyContain(v => v == 1000);
}
public void EDR_RecordsUserValue()
{
var reservoir = new DefaultForwardDecayingReservoir(
Constants.ReservoirSampling.DefaultSampleSize,
Constants.ReservoirSampling.DefaultExponentialDecayFactor,
_clock,
_scheduler);
reservoir.Update(2L, "B");
reservoir.Update(1L, "A");
reservoir.GetSnapshot().MinUserValue.Should().Be("A");
reservoir.GetSnapshot().MaxUserValue.Should().Be("B");
}
public void EDR_longPeriodsOfInactivityShouldNotCorruptSamplingState()
{
var reservoir = new DefaultForwardDecayingReservoir(
10,
0.015,
0.0,
_clock,
_scheduler);
// add 1000 values at a rate of 10 values/second
for (var i = 0; i < 1000; i++)
{
reservoir.Update(1000 + i);
_clock.Advance(TimeUnit.Milliseconds, 100);
}
reservoir.GetSnapshot().Size.Should().Be(10);
reservoir.GetSnapshot().Values.Should().OnlyContain(v => v >= 1000 && v < 2000);
// wait for 15 hours and add another value.
// this should trigger a rescale. Note that the number of samples will be reduced to 2
// because of the very small scaling factor that will make all existing priorities equal to
// zero after rescale.
_clock.Advance(TimeUnit.Hours, 15);
reservoir.Update(2000);
var snapshot = reservoir.GetSnapshot();
snapshot.Size.Should().Be(2);
snapshot.Values.Should().OnlyContain(v => v >= 1000 && v < 3000);
snapshot.Sum.Should().Be(snapshot.Values.Sum());
// add 1000 values at a rate of 10 values/second
for (var i = 0; i < 1000; i++)
{
reservoir.Update(3000 + i);
_clock.Advance(TimeUnit.Milliseconds, 100);
}
var finalSnapshot = reservoir.GetSnapshot();
finalSnapshot.Size.Should().Be(10);
snapshot.Sum.Should().Be(snapshot.Values.Sum());
finalSnapshot.Values.Skip(1).Should().OnlyContain(v => v >= 3000 && v < 4000);
}
public void ExponentialDecayingReservoir()
{
var reservoir = new DefaultForwardDecayingReservoir(
Constants.ReservoirSampling.DefaultSampleSize,
Constants.ReservoirSampling.DefaultExponentialDecayFactor);
foreach (var sample in _samples)
{
reservoir.Update(sample);
}
var snapshot = reservoir.GetSnapshot();
AssertValues(snapshot);
}
public void EDR_HeavilyBiasedReservoirOf100OutOf1000Elements()
{
var reservoir = new DefaultForwardDecayingReservoir(1000, 0.01);
for (var i = 0; i < 100; i++)
{
reservoir.Update(i);
}
reservoir.Size.Should().Be(100);
var snapshot = reservoir.GetSnapshot();
snapshot.Size.Should().Be(100);
snapshot.Values.Should().OnlyContain(v => 0 <= v && v < 100);
}
public void Update()
{
_reservoir.Update(_fixture.Rnd.Next(0, 1000), _fixture.RandomUserValue);
}